Over the past two decades, U.S. regulations dealing with bilgewater discharge for all types of vessels have grown increasingly stringent. Even the presence of an oil sheen is punishable under federal law. Environmental technology has struggled to keep pace, but until recently no removal method has been capable of eliminating sheen and extracting all harmful contaminants from bilgewater. Federal regulations set a high standard for bilgewater. Even the tiniest drop of bilgewater oil has been demonstrated to kill hundreds of thousands of lobster eggs, just one example of the enormous threat to all aquatic life.
The Federal Water Pollution Act—also known as the Clean Water Act—accordingly proscribes even the appearance of a visible sheen on the water, punishable by a $5,000 penalty. More specifically, the act “prohibits the discharge of oil or oily waste into or upon the navigable waters of the United States or the waters of the contiguous zone if such discharge causes a film or sheen upon, or causes a sludge or emulsion beneath the surface of the water.”
Further, under Sections 4301 (a) and (c) of the Oil Pollution Act of 1990, the fine for failing to notify the appropriate federal agency of a discharge has increased from a maximum of $10,000 to a maximum of $250,000 for an individual and $500,000 for an organization. The discharge of oil regulation, or “sheen rule,” establishes the following criteria for determining a harmful oil spill:                Discharges that cause a sheen or discoloration on the surface of a body of water;        Discharges that violate applicable water quality standards; or        Discharges that cause a sludge or emulsion to be deposited beneath the surface of the water or on adjoining shorelines.        
The sheen rule applies to both petroleum and non-petroleum oils—e.g., vegetable oil.
The discharge regulations also have been toughened for U.S. military vessels. The National Defense Authorization Act of 1996 amended Section 312 of the Federal Water Pollution Control Act to require the Secretary of Defense and the administrator of the U.S. Environmental Protection Agency (EPA) to develop UNDS for vessels of the armed forces for “discharges, other than sewage, incidental to normal operation”. Previously, this section only addressed the regulation of sewage.
From an environmental perspective, the increased regulatory activity in bilgewater discharge limits is warranted. The cumulative effect of vessels ranging from small recreational boats to large surface ships dumping even small amounts of bilgewater could wreak damage upon fragile aquatic ecosystems—and likely has already done so.
According to nature of discharge (NOD) reports obtained from the U.S. Navy, the composition of untreated bilgewater is a varying assortment of oil and grease, oxygen-demanding substances, and organic and inorganic materials. These materials, the reports say, include volatile organic compounds, semi-volatile organic compounds, inorganic salts and metals. The common metals collected in bilgewater samples include arsenic, copper, cadmium, chromium, lead, mercury, selenium and zinc, while organics include benzene, isomers of hexachlorocyclohexane, ethyl benzene, heptachlor, heptachlor expoxide, napthalene, phenols, pthalate esters, toluene, trichlorobenzene and trichloroethane.
The primary sources of these contaminants are vessel propulsion systems and auxiliary systems that use fuels, lubricants, hydraulic fluid, antifreeze, solvents and cleaning chemicals. Certain waste streams such as steam condensate, boiler lowdown, drinking fountain water, and sink drainage located in various machinery spaces can also drain to the bilge.
In worst-case scenarios, environmentally irresponsible vessel operators have dealt with excess bilgewater by dumping it overboard. Others have tried to hide the telltale sheen with emulsifiers, though the damage is still done.
Currently, commercial and military surface ships primarily employ two different methods in dealing with bilgewater treatment and removal. Many of these vessels use oil water separator systems to reduce the oil content of bilgewater prior to overboard discharge. Most of these large vessels also have onboard systems for collecting and transferring bilgewater to a holding tank for later removal and disposal on shore.
In the present inventor's U.S. Pat. No. 6,475,393 (also see related U.S. Pat. No. 6,180,010) it is disclosed that the compositions described in the inventor's U.S. Pat. Nos. 5,437,793; 5,698,139; and 5,837,146, and 5,961,823 (all of which disclosures are hereby incorporated by reference) have extremely strong affinities for the aforementioned contaminants in oily bilgewater; and that when oily bilgewater streams containing these noxious contaminants are passed through filtration media incorporating these compositions, the contaminants are immobilized at the media, as a result of which concentration levels of the contaminants in the filtrate may be reduced to very low values, in some instances below detectable limits in a single pass. This not only enables ready removal from the bilgewater of oils, greases and the like, but as well, removal of pernicious slightly soluble organic compounds such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, etc. These noxious contaminants are among the more difficult compounds to remove from water, and indeed most are carcinogenic. The solubility of the foregoing substances renders most prior art physical separation methods ineffective and causes formation of stable and pseudostable oily emulsions (micelle size of 400 micrometers or less), which also don't respond well to gravity separation due to neutral buoyancy.
In accordance with these prior inventions, the bilgewater is passed through one or more filters incorporating the principles of the earlier inventions, prior to the bilgewater being actually discharged from the vessel. The filter or filters may simply be placed directly in the bilgewater discharge line, e.g. downstream of the bilgewater pump effecting the discharge flow. In a test of a typical such installation, the test results included removal of all sheen and visible discharge.
More specifically the method of the prior invention may be described as one of passing the bilgewater through a fluid-pervious filtration media which has been infused with an absorbtion composition comprising a homogeneous thermal reaction product of an oil component selected from the group consisting of glycerides, fatty acids, alkenes, and alkynes, and a methacrylate or acrylate polymer component; the contaminant being thereby immobilized at the media. Filter configurations incorporating the above described compositions (hereinafter referred to as “absorbent compositions”) may be based on various water permeable substrates, such as shredded, spun or otherwise configured polypropylene or shredded or spun cellulose, which substrates are infused or otherwise treated with the absorbent compositions, which are then cured. These substrates may then be packed or otherwise disposed in a cartridge or canister filter; or can be formed into cured and infused bag filters which can be emplaced in canisters through which the contaminated bilgewater is flowed. Similarly the said absorbent compositions can be incorporated into or upon other filtering substrates and media, such as paper, including compressed pulp materials, particulate porous foamed plastics, mineral particulates such as perlite and vermiculite, and particulate, fibrous or porous ceramic or porous (e.g. sintered) metal substrates and media.
It should be appreciated that the use herein of the term “absorbent composition” is one of convenience for identifying the compositions of my aforementioned patents. The specific mechanism by which the noxious contaminants are removed from the bilgewater streams by conjunctive use of the “absorbent compositions” is not completely understood, and could include attachment and/or fixation of such contaminants by mechanisms which technically involve various physical and/or chemical interactions. The term “absorbent” as used herein is intended to encompass all of these possible mechanisms.
In the course of utilizing bilgewater filtration systems, including those based upon the foregoing principles, it is often difficult to determine the quality of effluent from oily water separators without relying on sensor readings. It is often not possible even to determine visually if the unit is on or off. Inability to perform visual inspection has resulted in accidental oily bilge water discharge and even criminal prosecution. In the case of oily water treatment devices it is not possible to effectively use transparent sight gauges or glass indicators on the housings or in the connecting piping due to the tendency of the surfaces over which the discharge flows to become opaque from oily fouling.